In this project we hope to learn something of the mechanism by which genetic information is repressed and derepressed, by studying the amounts, structures, and rate of synthesis of chromosomal materials, in particular the histones and tubulin. The study will be carried out on material derived from tissues which are in different phases of genetic expression. The amino acid sequences of several Hl histones are being determined, and the interaction of individual Hl histones with chromatin fragments will be determined by circular dichroism, filter binding and sedimentation. The role of GTP/GDP binding in the assembly of tubulin will be investigated by correlation between assembly and chemical modification. A new method will be developed for the isolation of mitotic apparatus. The new type of isolate will be characterized.